1. Field of the Invention
The present invention relates to computers. More specifically, the invention relates to a switch device in a computer and an associated method of operation for notifying an hot-plug interface of insertion and removal of an adapter card.
2. Description of the Related Art
Computer systems communicate with various peripheral devices and other computer systems via communication buses. The peripheral devices are generally connected to the communication buses by an adapter card. Communication buses are generally fault-intolerant so that a failure of an adapter card may have a wide range of effects on system performance. In some cases, adapter card failure may prevent subsequent bus transactions. Some failures may corrupt main memory. Sometimes failure may result in the loss of only a single, localized network connection. Often, the effects are unpredictable.
A common cause of system failure is the accidental accessing, by removing or installing, adapter cards from a card slot connected to a communication bus while the card slot is powered and running. Although system manufacturers, systems administrators, and others warn of the dire consequences of adapter card manipulation while the card slot is powered, occasionally a card is accidentally removed or added while the slot is powered, typically resulting in failure of the server and loss of productive work by staff.
To prevent system failure due to card removal or addition while a slot is powered, a "Hot-Plug" specification has been adopted which sets forth devices and structures to allow insertion and removal of adapter cards from a powered communication bus. One such specification is a PCI (Peripheral Communication Interface) Hot-Plug specification which sets standards for aspects of removal and insertion of PCI adapter cards while the system is running. The Hot-Plug specification is applicable to desktop computers, portable systems, target server platforms, and the like.
Operating systems that are widely used in the computing industry are not generally designed to tolerate unexpected removal of devices. The Hot-Plug specification has thus been created to define a sequence of user actions and system management facilities that inform the operating system of a desire to remove an adapter card. The actual removal is not to occur until the software system acknowledges readiness.
In addition, adapter cards are not generally designed to be connected to a slot that is already powered. Accordingly, the Hot-Plug specification defines a sequence of user actions and system behavior to ensure the removal of power to a slot before a card is inserted into the slot.
The insertion or removal of an adapter card without following the proper sequence may cause unpredictable results, including data corruption, abnormal termination of the operating system, damage to the adapter card, or damage to platform hardware.
What is needed is an interface device and associated operating method that simply, conveniently, and inexpensively ensure that power is removed from a slot during removal and insertion of an adapter card.